A house in Mobile, Ala., was damaged after a tornado touched down on Christmas Day. / Mike Kittrell, AP

by Bart Jansen, USA TODAY

by Bart Jansen, USA TODAY

A powerful winter storm is forecast to slam Pennsylvania and the Northeast on Thursday, after killing six people while hurling tornadoes across the South and blanketing the Midwest in snow the past two days.

In Indiana, 40 vehicles got bogged down trying to make it up a slick hill on state Highway 37 near Bloomington, which got more than 11 inches of snow. Four state snowplows slid off roads as snow fell at the rate of 3 inches an hour in some places.

The storm, which dumped 7 inches of snow on Indianapolis and on Youngstown, Ohio, could bring 12 to 18 inches of snow as it moves across northern Pennsylvania, upper New York state and New England, according to the National Weather Service.

The weather service also forecasts heavy rain along the coastline south to the Mid-Atlantic. Strong winds of 50-60 mph are expected across the region before the storm crosses into Canada and over the Atlantic Ocean.

"This will be the third and final day of the storm's trek across the eastern third of the country," said Chris Vaccaro, a weather service spokesman.

Blizzard conditions across Indiana and Ohio played havoc with traffic Wednesday.

"We've had numerous crashes all across the state of Ohio, with periodic road closures," said Lt. Anne Ralston, a state highway patrol spokeswoman.

"Sometimes we can't move it as fast as it falls," said Jarrod Bolden, superintendent of Cincinnati's traffic and road operations

In Indiana, 40 vehicles got bogged down trying to make it up a slick hill on state Highway 37 near Bloomington, which got more than 11 inches of snow. Four state snowplows slid off roads as snow fell at the rate of 3 inches an hour in some places.

The storm prompted airlines to cancel 1,839 flights between early Tuesday and 4:30 p.m. Wednesday at airports from Texas to New York, according to FlightAware.com, which tracks flights. The number was expected to rise "significantly" as the storm rolled overnight into New York City, where 50-mph wind is forecast, according to Daniel Baker, FlightAware's chief executive.

Most of the canceled flights Wednesday were at Dallas/Fort Worth with 265; Philadelphia, 214; and Indianapolis, 150. Other airports with dozens of cancellations included Ohio's Cincinnati, Columbus and Akron; New York City area's LaGuardia, JFK and Newark; and Washington's Dulles and Reagan National.

Carlo Bertolini, spokesman for the Indianapolis airport, said the airport got mats for travelers to sleep on if they were stranded, and asked restaurants to stay open later. But because most passengers start or end their trips at the airport, Bertolini didn't expect many people to stay overnight.

"We'll be ready if that's the case," Bertolini says.

Victoria Wigsmoen, 21, got up early Wednesday to drive through heavy snow to the Indianapolis airport for a trip to Orlando. But her 11 a.m. departure was among the sea of red cancellations on the departure board.

"At least I can still spend New Year's Eve in Disney," Wigsmoen says.

Dozens of reported tornadoes and high winds around the Gulf Coast region killed motorists and damaged property.

The weather service is investigating reports of 39 tornadoes Tuesday across Texas, Louisiana, Mississippi and Alabama. Another two were reported Wednesday in eastern North Carolina.

Two passengers in a car on a sleet-slickened Arkansas highway were killed Wednesday in a head-on collision, and two people, including a 76-year-old Milwaukee woman, were killed Tuesday on Oklahoma highways. Deaths from wind-toppled trees were reported in Texas and Louisiana.

In Arkansas, some of the nearly 200,000 people who lost power could be without it for as long as a week because of snapped poles and wires after ice and 10 inches of snow coated power lines, said the state's largest utility, Entergy Arkansas.

Gov. Mike Beebe sent out National Guard teams, and Humvees transported medical workers and patients. Snow hadn't fallen in Little Rock on Christmas since 1926, but the capital ended Tuesday with 10.3 inches of it.

Other states also had scattered outages. Duke Energy said it had nearly 300 outages in Indiana. More than 100,000 customers had lost power Tuesday in Texas, Arkansas, Oklahoma, Mississippi, Louisiana and Alabama.

Behind the storm, Mississippi declared states of emergency in eight counties with more than 25 people reported injured and 70 homes left damaged by high winds or tornadoes.High winds toppled a tree onto a pickup in the Houston area, killing the driver, and a 53-year-old northern Louisiana man was killed when a tree fell onto his house.

Two passengers killed when their car crossed the center of an Arkansas highway in sleet Wednesday and struck an SUV head-on.

Icy roads were blamed for a 21-vehicle pileup in Oklahoma. A 28-year-old woman was killed in a crash on a snowy highway near Fairview, Okla. A 76-year-old Wisconsin woman who was a passenger in a car on Interstate 44 in Oklahoma that hit a pickup head-on was killed.

In Mobile, Ala., wind damaged homes, a high school and a church, and knocked down power lines.

Rick Cauley, his wife, Ashley, and two children were hosting members of both of their families. When the sirens went off, the family headed down the block to take shelter at the athletic field house at Mobile's Murphy High School.

"As luck would have it, that's where the tornado hit," Cauley said. "The pressure dropped and the ears started popping and it got crazy for a second."